Strike-slip Faulting Energy Release

Lingling Ye, Hiroo Kanamori, Thorne Lay, & Jean-Philippe Avouac

Published May 10, 2017, SCEC Contribution #6899, 2017 SCEC Annual Meeting Poster #243

Teleseismic recordings of P waves from 26 large (mostly, MW ≥ 7.5) strike-slip earthquakes from 1990- 2015 have been analyzed to determine their radiated energy, ER, exploring the stability of the estimates with respect to the faulting geometry and directivity. The radiated energy estimates demonstrate that moment-scaled radiated energy ER/M0, for strike-slip events is systematically higher than found for large megathrust events. Finite-fault inversions for several of the events have been performed to resolve the spatial extent of faulting and to calculate the stress drops, supplementing published estimates for other events. The effects of rupture directivity (deviation from point-source radiation patterns) for the non-uniform slip models have been assessed for several large ruptures by examining azimuthal patterns of individual station ER estimates. The source directivity effect on single-station ER measurements is generally relatively weak, but systematic variation as a function of directivity parameter can be detected for several events. A factor of ~2-3 azimuthal trend is observed for most supershear events, and bias of the average value can be avoided by azimuthal sampling. This effect appears modest, but one must consider the narrow cone of teleseismic P wave paths from the source and their proximity to the nodal planes of strike-slip focal mechanisms. There are also complexities in each rupture and directivity effects are not the extreme end-member cases expected for simple uniform unilateral ruptures. In addition, we estimate the radiated energy for moderate earthquakes in Japan and South California with dense regional seismic network to evaluate the uncertainty in radiated energy measurements.

Ye, L., Kanamori, H., Lay, T., & Avouac, J. (2017, 05). Strike-slip Faulting Energy Release. Poster Presentation at 2016 SCEC Annual Meeting.

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